What to Know When Towing with Heavy-Duty Diesel Trucks

Heavy-duty diesel pickups are most at home when doing jobs like towing. These beasts-of-burden are happiest when saddled with loads. Today’s class of extraordinary heavy-duty trucks offers diesel torque of up to 1,200 lb-ft and maximum tow ratings of 20 tons. And here’s the craziest part: they’ll let anyone purchase one.

towing mirrors

For this reason, it is critical that each new owner should learn the basics of trailering before hitching up the first load. Knowing and understanding the most critical aspects of the craft will ensure a safer and less stressful towing experience. Proper preparation, regular maintenance, and adherence to safety practices are key to preventing accidents and prolonging the lifespan of both the trailer and tow vehicle.

Before we head out into the real world, let’s dive into some of the most misunderstood and commonly overlooked aspects of trailer towing.

fifth-wheel towing

2024 Ram 3500 Heavy Duty Tradesman Regular Cab Dually

Understanding Your Truck’s Towing Specifications

There are three figures that are more important when it comes to towing than the simple maximum tow rating that is often advertised. These massive figures, while impressive on paper, typically exist on only a single configuration of pickup that may not even be orderable by the public. Every truck on the road is going to have a different maximum tow rating. These can sometimes be found in the vehicle’s owner’s manual or the manufacture’s website. However, the most accurate way to prevent overloading is to get the true curb weight of your truck from a certified scale and subtract that number from the truck’s Gross Combined Weight Rating.

That brings us to the second important specification: Gross Combined Weight Rating (GCWR). Every truck has a maximum GCWR. However, this figure is at times difficult to locate. While some manufacturers print the number on a door jamb sticker, others place it in the owner’s manual or website. The GCWR is the total allowable weight of the vehicle, trailer, cargo, and passengers combined. Subtracting the curb weight of the truck (along with the total of cargo and passengers) from the GCWR will yield the actual maximum tow rating.

The third, and often misunderstood, towing specification is a truck’s Gross Vehicle Weight Rating (GVWR). GVWR is the maximum allowable weight of the truck, without a trailer attached. This figure includes the truck’s curb weight along with all passengers and cargo. At times, loading five adults into the cab of a pickup will get close to (if not exceed) its maximum GVWR. It’s also important to know that when towing, the trailer’s tongue weight gets applied to and subtracted from the truck’s maximum GVWR.

fifth wheel towing

Driver front 3/4 view of 2023 GMC Sierra 3500HD towing a fifth wheel

Choosing the Correct Trailer Hitch

There are three basic categories of trailer hitches that can be used with a heavy-duty pickup: conventional, fifth-wheel, and gooseneck. Choosing the type of hitch to be used is largely dictated by the trailer. However, within these hitch categories there are many different types and options.

Conventional trailer hitch receivers are the ones most often thought about, which mount to the rear frame of the truck and hang below the rear bumper. These hitches are typically broken down into five different class categories. These include Class I (up to 2,000 pounds), Class II (up to 3,500 pounds), Class III (up to 8,000 pounds), Class IV (up to 10,000 pounds), and Class V (over 10,000 pounds). Heavy-duty pickups will come equipped with either a Class IV or V hitch from the factory.

Weight distributing trailer hitches are often used along with a conventional hitch receiver. For large loads with heavy tongue weight, these hitches work to evenly distribute the trailer’s tongue weight across the truck’s two axles, which improves both stability and control. It’s worth remembering that using a weight distributing hitch does not increase towing capacity.

fifth wheel towing

The second type of trailer hitch most often used with heavy-duty pickups is a fifth-wheel hitch. Fifth-wheel hitches are designed for hauling large, heavy trailers such as travel trailers, horse trailers, and large utility trailers. They are mounted in the bed of a pickup truck and utilize a secure kingpin connection. In addition to offering greater load carrying capacity than a conventional hitch receiver, fifth-wheel hitches also provide enhanced maneuverability, increased stability, and better weight distribution by placing the trailer’s hitch weight directly over the rear axle.

Depending on the type of trailer and bed length, there are several models of fifth-wheel hitches to choose from. These include a fixed fifth-wheel hitch that offers a solid, stationary connecting point. Sliding fifth-wheel hitches are designed for short-bed trucks and allow the hitch to slide back when making sharp turns to prevent the trailer from hitting the cab. And finally, there are pivoting fifth-wheel hitches that tilt in multiple directions to accommodate uneven terrain.

Finally, there is the gooseneck hitch. Gooseneck trailer hitches are designed for hauling very large trailers such as livestock, utility, and vehicle haulers. These are particularly popular in agriculture, commercial, and industrial settings. Similar to fifth-wheel hitches, gooseneck hitches mount in the beds of pickup trucks. However, instead of a kingpin, the gooseneck hitch utilizes a ball that is typically located over (or slightly in front of) the rear axle. Gooseneck hitches offer the highest levels of trailer towing weight and are typically needed to achieve a heavy-duty pickup’s maximum tow rating. Like fifth-wheel hitches, goosenecks also offer increased stability and maneuverability over conventional hitch receivers.

towing

2024 Ram 2500 Heavy Duty Big Horn Mega Cab

Trailer Balance and Weight Distribution

Once you know your truck’s maximum rated ability and have chosen the proper hitch, it’s time to set up the trailer. Setting a proper tongue weight is imperative to a safe and enjoyable towing experience. Tongue weight is the downward force exerted on the hitch by the trailer. Ideally, tongue weight should be between 10 and 15 percent of the total trailer weight to ensure stability. Too little tongue weight can cause undue trailer sway, while too much can overload the rear axle and reduce steering ability.

Directly affecting tongue weight is a trailer’s weight distribution. Heavier items should be located low and centered over the trailer axles. Placing the load too far forward will increase tongue weight, while too far to the rear will lessen the tongue weight.

If a trailer’s tongue weight exceeds the tow vehicle’s available payload (GVWR minus curb weight and people/cargo), it shouldn’t be towed by that pickup. For example, some ¾-ton diesel trucks may offer a tow rating of more than 20,000 pounds but have a payload rating of less than 2,000 pounds. This means that even with just a single driver, a proper tongue weight of 10 percent will push the truck over its rated payload limit.

Passenger front 7/8 view of 2023 GMC Sierra 2500HD SLT Crew Cab in Onyx Black hauling ATVs with mountains in background

Trailer Braking Systems

Getting a trailer moving is one thing, but slowing it down safely is arguably more important. Most heavy trailers come equipped with their own braking systems, which are typically electric. Newer heavy-duty pickups also come with built-in electronic brake controllers. However, if your truck doesn’t have one, there are many aftermarket options available. The electronic brake controller works by synchronizing the trailer’s brakes with the towing vehicle’s brakes, ensuring that the trailer slows at the same rate as the tow vehicle. In addition to electronic trailer brakes, there are also electric-over-hydraulic systems along with hydraulic surge brakes (typically utilized on watercraft trailers).

trailer brake

Towing Safety Practices and Legal Regulations

There are a few basic safety and regulatory items that all people should know before towing their first loads. Before each trip it is important to inspect both the trailer and towing vehicle to ensure that everything is in proper working condition. This includes inspecting the tire tread and pressure, all lights, the hitch connection, and the braking system. It’s also important to properly secure all cargo by ensuring that everything is properly fastened to prevent shifting during transit.

When towing a heavy trailer, it’s important to adjust your driving style accordingly. Accelerating gradually will help to protect the truck, trailer, and cargo from shock loads. The heavier the load, the more power and time it will take to get up to cruising speed. It’s also important to begin braking early, as the increased weight will lengthen needed stopping distance, even with trailer brakes. You’ll also need to increase the following distance between your tow vehicle and those in front of you. Trailers also have a larger turning radius than the truck towing them, requiring wider turns to avoid curbing wheels or clipping obstacles.

It is important to know and adhere to local speed limits for vehicles towing trailers. These limits can often be lower than that of normal traffic. In some instances, such as the state of California, there is a statewide maximum trailer speed limit. In addition to exposing the driver to unnecessary interactions with local law enforcement, excessive speed can also increase the risk of trailer sway and reduce braking efficiency.

When towing especially heavy loads, it’s important to know what local weight limits may be in place, if towing permits are required, what safety equipment must be carried onboard, and if there are any special licensing requirements. Most drivers either ignore or are ignorant of licensing requirements, as even a modestly sized recreational vehicle may require a commercial license.

Lastly, today’s new trucks are equipped with tons of towing technology that can be helpful, if you know how to use these systems. Familiarize yourself with your truck’s towing tech before hitting the road, since distracted towing is the last thing anyone wants. Practice using the systems in uncrowded, stress-free situations so that you’ll know exactly what to do when the pressure’s on. Be aware of diesel exhaust fluid consumption, and have a replenishment plan if necessary.

Happy towing!

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